1. Field of the Invention
The present invention relates to a base film including a magnetic recording layer and an antistatic layer (i.e., a conductive layer) and, in particular, to a base film having an adhesion layer disposed between the substrate and the antistatic layer, and photographic elements including the same.
2. Background of the Invention
The use of polymeric film bases for carrying photographic layers is well known. In particular, photographic elements which require accurate physical characteristics use polyester film bases, such as poly(ethylene terephthalate) film bases, and cellulose ester film bases, such as cellulose triacetate film bases.
In recent years, with the development of rapid film processing labs, the amount of information that would be desirable to record and read on a photographic element has increased. For example, it may be desirable to record information relating to the element's sensitivity, exposure conditions (e.g., exposure time and f-stop value), date and time of exposure, name of photographer, various messages related to the development and printing (e.g., number of reprints, portion to be zoomed, and the like) of the photographic element.
Thus, it is known to provide a magnetic layer in a photographic element for recording such information. In such a photographic element, typically a silver halide portion of the element is employed to record images by customary photographic process while the magnetic layer is employed by techniques similar to those employed in the magnetic recording art. However, the requirements of recording and reading magnetic signals from a magnetic layer in a photographic element are typically more stringent than that found in conventional magnetic recording because of the loading of magnetic particles in the magnetic layer and the nature of the photographic element. Further, the presence of the magnetic layer cannot interfere with the primary function of the photographic element which is to achieve realistic visual reproductions of the original image. In addition, the magnetic layer must be capable of accurately recording the information applied thereto and reproducing (reading) the information on demand.
In addition, a photographic element including a magnetic layer should be capable of repeated use in both the recording and reading modes, and, therefore, photographic element should be sufficiently durable. For example, during the residence of the film in a camera, entries may be made to the magnetic layer for every exposure, and an indeterminate number of read operations are conducted depending on the particular application for which the film is used. This is particularly true in the processing of film and in subsequent use of the processed film for additional copies, where the film is typically wound under tension in a liquid environment. In some instances, it is reasonable to expect that the film must be able to withstand multiple contacts with magnetic heads, sometimes 50 operations or more.
Further, the formation of static electric charges on the film base can be a serious problem in the production of photographic elements. While coating the light-sensitive emulsion, electric charges which accumulate on the base discharge, producing light which is recorded as an image on the light-sensitive layer. Other drawbacks which result from the accumulation of electric charges on polymeric film bases are interference with magnetic data recording and reading, the adherence of dust and dirt, coating defects and limitation of coating speed.
Additionally, photographic elements comprising light-sensitive layers coated onto polymeric film bases, when used in rolls or reels, which are mechanically wound and unwound, or in sheets, which are conveyed at high speed, tend to accumulate static charges and record the light generated by static discharges. Moreover, charge buildup can create difficulties in processing, such as jamming as the photographic films are fed through processing equipment.
The static-related damages occur not only before the photographic element has been manufactured, exposed, and processed, but also after processing when the photographic element including the image is used to reproduce and enlarge the image. Accordingly, it is desired to provide permanent antistatic protection which retains its effectiveness even after processing.
To overcome the adverse effects resulting from accumulation of static electrical charges, photographic elements are provided with antistatic layers including electrically conductive materials which are capable of transporting charges away from areas where they are not desired. Typically, such antistatic layers contain electrically conductive substances, in particular polyelectrolytes such as the alkali metal salts of polycarboxylic acids or polysulfonic acids, or quaternary ammonium polymers, which dissipate the electrical charge by providing a surface which conducts electricity by an ionic mechanism. However, such layers are not very suitable as antistatic layers because they lose effectiveness under conditions of low relative humidity, become sticky under conditions of high relative humidity, and lose their antistatic effect after passage through photographic processing baths.
Antistatic materials that conduct electrons by a quantum mechanical mechanism rather than ions by an ionic mechanism are preferred because antistatic materials that conduct electrons by a quantum mechanical mechanism are effective independent of humidity. They are suitable for use under conditions of low relative humidity, without losing effectiveness, and under conditions of high relative humidity, without becoming sticky. Defect semiconductor oxides and conductive polymers have been proposed as electronic conductors which operate independent of humidity. A major problem, however, with defect electronic conductors is that they generally cannot be provided as thin, transparent, relatively colorless coatings by solution coating methods.
Vanadium oxide antistatic coatings have been taught for use in photographic elements. See, U.S. Pat. Nos. 5,702,876 and 5,709,985 (both to Morrison et al.) for discussions related to vanadium oxide antistatic coatings in photographic elements that can either be located on the emulsion side or the back side of the photographic element. For example, the antistatic layer comprising vanadium oxide located on the back side of the photographic element (i.e., on the side of the film base opposite to the image-forming light-sensitive halide emulsion layer) as outermost layer, with or without a protective abrasion-resistant topcoat layer; or it can be located as a subbing layer underlying a silver halide emulsion layer or an auxiliary gelatin layer. For example, U.S. Pat. No. 5,006,451 (Anderson et al.) describes a photographic material comprising a film base having thereon an antistatic layer comprising vanadium oxide and a barrier layer which overlies the antistatic layer.